Folding baby stroller system and method

ABSTRACT

A baby stroller for transporting an infant at speeds faster than normal walking is disclosed. This baby stroller can be folded to make it easier to stow and transport. The folding mechanism, a unique feature of the design is directed toward compactness, ease of use, reliability, and reduction in manufacturing costs.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority under 35 U.S.C. § 120 to pending U.S. patent application Ser. No. 15/834,972, titled “Folding Baby Stroller System and Method,” filed on Dec. 7, 2017, which is a continuation of and claim priority to U.S. Pat. No. 9,862,400, titled “Folding Baby Stroller System and Method,” filed on Sep. 5, 2013, which is a continuation of and claims priority to U.S. Pat. No. 8,550,489, titled “Folding Baby Stroller System and Method,” filed on Jun. 15, 2012, which is a continuation of and claims priority to U.S. Pat. No. 8,226,111, titled “Folding Baby Stroller System and Method,” filed on Aug. 17, 2010, which is a continuation of and claims priority to U.S. Pat. No. 7,798,515, titled “Folding Baby Stroller System and Method,” filed on Mar. 3, 2008, which is a continuation of and claims priority to U.S. Pat. No. 7,396,039, titled “Folding Baby Stroller System and Method,” filed on Oct. 20, 2005, which is a continuation of and claims priority to U.S. Pat. No. 6,991,248, titled “Folding Baby Stroller System and Method,” filed on May 5, 2003, the entire contents of each of which is incorporated by reference herein in its entirety for all purposes.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to baby strollers, and more particularly, to all-terrain baby strollers that can be folded.

Description of the Related Art

Traditionally, baby strollers have been used to push an infant slowly on a relatively hard, smooth floor or sidewalk. As a result, the strollers were made small and light. These strollers work well enough at slow speed, but are extremely unwieldy and even dangerous on rough surfaces or at higher speeds.

All-terrain baby strollers have been designed to overcome these problems. These strollers typically employ much larger wheels, often large bicycle tires. The stroller frame members are constructed of metal tubular stock and durable plastic frame connectors or other durable material to connect the frame members together to handle the heavy duty use they may receive. The frame connectors are used also to rotate or pivot one frame member relative to another, and are used to removably connect other frame members together.

Some advanced designs of all-terrain strollers have allowed for a certain degree of folding of the all-terrain baby strollers into less than a desirable amount of compactness. In addition, conventional folding mechanisms include complications that increase cost and reduce reliability and ease of use.

BRIEF SUMMARY OF THE INVENTION

The present invention resides in a folding baby stroller system and method. Embodiments include a front wheel and left and right side laterally spaced-apart front wheel supports. Each of the left and right side front wheel supports has a forward end portion and a rearward end portion. The front wheel is mounted to the forward end portion of at least one of the front wheel supports, the left and right side front wheel supports being rotatable as a unit. Further included are left and right rear wheels, and left and right side laterally spaced-apart rear wheel supports. Each of the left and right side rear wheel supports has a lower end portion and an upper end portion, the lower end portions being coupled to at least one of the left and right rear wheels. Further included are left end right side laterally spaced-apart handle members. Each of the left and right side handle members has a forward end portion and a rearward end portion with a handle portion, the left and right side handle members being rotatable as a unit. Further included are left and right side laterally spaced-apart folding assemblies. Each of the left and right side folding assemblies has a first rotatable member and second rotatable member rotatably coupled to a pivot member supported by the upper end portion of a corresponding one of the left and right side rear wheel supports for rotation about a common axis of rotation and independently rotatable relative to each other. The rearward end portion of a corresponding one of the left and right side front wheel supports is fixedly attached to the first rotatable member, and the forward end portion of a corresponding one of the left and right side handle members is fixedly attached to the second rotatable member.

Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an isometric view of an exemplary implementation of a baby stroller embodying the present invention shown in a fully unfolded state ready for usage.

FIG. 2 is an isometric view of the stroller frame of FIG. 1 without a seat and a leg guard.

FIG. 3 is a front elevational view of the stroller frame of FIG. 2.

FIG. 4 is a side elevational view of the stroller frame of FIG. 2.

FIG. 5 is a front elevational view of the stroller frame of FIG. 2 shown in a partially folded state with left and right front supports being rotated about their respective side folding assemblies toward respective side rear wheel supports.

FIG. 6 is a side elevational view of the stroller frame of FIG. 2 shown in the partially folded state of FIG. 5.

FIG. 7 is a side elevational view of the stroller frame of FIG. 2 shown in a fully folded state with both left and right front supports and left and right side handle supports being rotated about their respective side folding assemblies toward respective side rear wheel supports.

FIG. 8 is an exploded isometric view of one of left and right side folding assemblies of the implementation shown in FIG. 1.

FIG. 9 is an enlarged, fragmentary, side elevational view of the stroller frame of FIG. 2 in the fully unfolded state better illustrating one of the side folding assemblies.

FIG. 10 is a side elevational view of the stroller frame in the fully unfolded state of FIG. 9 showing internal components of one of the side folding assemblies.

FIG. 11 is the side elevational view of the stroller frame in the fully unfolded state of FIG. 9 with the internal components of the side folding assembly shown in broken line.

FIG. 12 is the side elevational view of the stroller frame of FIG. 11 in the fully folded state with the internal components of the side folding assembly shown in broken line.

DETAILED DESCRIPTION OF THE INVENTION

As shown in the drawings for purposes of illustration, the present invention is embodied in an all-terrain baby stroller 10, as shown in FIG. 1, having a foldable, tubular metal frame 12 and a transversely extending rear axle assembly 14 with a transverse, non-rotating tubular rear axle 15. Left and right side rear wheels 16 are rotatably mounted to the ends of the rear axle assembly 14. The forward end of the frame 12 has a single front wheel 18 rotatably mounted thereto.

The frame 12 has no base frame members extending rearwardly from the front wheel 18 to the rear axle assembly 14 as do most conventional all-terrain strollers. Instead, the frame 12 includes left and right side, downwardly and forwardly sloping front wheel frame members or supports 20, which each extend downward from a corresponding one of left and right side folding assemblies 22 in a converging configuration to the front wheel 18. A forward free-end 20 a of each of the left and right side front wheel supports 20 has a plastic front wheel connector (not shown) fixedly attached thereto and a corresponding one of the left and right ends of an axle 18 a of the front wheel 18 removably attached thereto to mount the front wheel to the stroller frame 12.

The front wheel supports 20 are interconnected by a foot rest 28 that spans between them toward but rearward of their forward free-ends 20 a and that is fixedly attached to each at a position just above the front wheel 18 and just rearward of the axle 18 a of the front wheel. As a result of the interconnection provided by the foot rest 28, and also the front wheel 18 when attached to the left and right side front wheel connectors, the left and right side front wheel supports 20 form a stationary unit with respect to the left and right side folding assemblies 22 upon folding and unfolding of the stroller 10, as will be described in greater detail below.

The frame 12 also includes left and right side upwardly and rearwardly sloping handle frame members or supports 24, which each extend upward from the corresponding one of the left and right side folding assemblies 22 in a generally parallel configuration to a handle 26 extending between the left and right side handle supports. The handle 26 is covered by a foam grip. The handle supports 24 are interconnected by the handle 26 that spans between them at their rearwardmost and uppermost extension and that is fixedly attached to each.

As a result of the interconnection provided by the handle 26, the left and right side handle supports 24 move as a unit with respect to the left and right side folding assemblies 22 upon folding and unfolding of the stroller 10, as will be described in greater detail below. It is noted that in lieu of the interconnecting handle 26, the handle supports 24 may each be provided with a handle portion at the upper end thereof such as used with umbrella style strollers.

In the illustrated embodiment of the invention the left and right side handle supports 24 and the handle 26 are formed as an integral unit by bending a single length of aluminum tube. The left and right side handle supports 24 are movable relative to the left and right side front wheel supports 20 for folding of the stroller 10 and do not together form an integrated rigid upper frame. The left and right side handle supports 24 are also movable independent from movement of the left and right side front wheel supports 20.

The frame 12 also includes left and right side, downwardly and rearwardly sloping rear wheel frame members or supports 30, which each extend downward from the corresponding one of the left and right side folding assemblies 22 in a generally parallel configuration to the rear axle assembly 14. A rearward free-end 30 a of each of the left and right side rear wheel supports 30 is fixedly attached to a corresponding one of the left and right ends of the tubular rear axle 15. The rear wheel supports 30 are interconnected by the rear axle assembly 14 that spans between them at the rearward free-ends 30 a thereof. As a result of the interconnection provided by the rear axle assembly 14, the left and right side rear wheel supports 30 move as a unit with respect to the left and right folding assemblies 22 for folding and unfolding of the stroller 10, as will be described in greater detail below. The left and right side rear wheel supports 30 are also movable relative to the left and right side front wheel supports 20 and the left and right side handle supports 24 for folding of the stroller 10. Further, the left and right side rear wheel supports 30 and the rear axle assembly 14 connected thereto do not form a part of a base frame extending between the rear and front wheels 16 and 18. Much of the structural strength of the stroller 10 and the interconnection of the forward wheel supports 20, the handle supports 24, and the rearward wheel supports 30 are provided by the centrally positioned left and right side folding assemblies 22, and not by a base frame.

In the illustrated embodiment of the stroller 10, the left and right side front wheel supports 20, the left and right side handle supports 24, and the left and right side rear wheel supports 30 are made from aluminum tube. Suitable alternative materials may be used.

The left and right outward ends of the tubular rear axle 15 are open and internally threaded to receive a threaded stub axle 32 forming a part of the corresponding one of the left and right rear wheels 16. A lock nut (not shown) when tightened against the face of the stub axle 32 locks the stub axle against loosening during usage of the stroller 10. Alternative constructions may be used to fixedly or removably attach the rear wheels 16 to the tubular rear axle 15, and any suitable alternative manner of mounting the rear wheels 16 to the real wheel supports 30 may be used with or without a park brake.

The frame 12 of the stroller 10 is shown in FIG. 1 in the fully unfolded state with a fabric seat 2, fabric leg support and guard 3. For purposes of illustration, the frame 12 is shown in FIG. 2 without the seat 2 and the leg guard 3. The seat 2 is suspended from the left and right side handle supports 24, and the leg guard 3 spans between and is supported by the left and right side front wheel supports 20.

For the depicted implementation, user operation of the left and right side folding assemblies 22 will now be described. The left and right side folding assemblies 22 have the same construction, and the description below while in the singular is applicable to both. Each of the left and right rear wheel supports 30 supports an inwardly extending lever 34, which has a predominantly vertical orientation, as shown in FIG. 3, when the frame 12 of the stroller 10 is locked in the fully unfolded position. To begin the procedure to fold the frame 12, each of the levers 34 are pulled upward and inward as depicted by arrows R1 to thereby put the folding assemblies 22 in an unlocked state as further explained below. With each of the left and right folding assemblies 22 in an unlock state as further explained below.

With each of the left right folding assemblies 22 in an unlocked state, the left and right handle supports 24, along with the handle 26, and the left and right forward wheel support 20, along with the forward wheel 18, can be rotated about the left and right folding assemblies, respectively, toward the left and right rear wheel supports 30, respectively, as depicted by arrows R2 shown in FIG. 4. As stated, the forward wheel supports 20 can be moved independently from movement of the handle supports 24. In the process of folding the frame 12, if the forward wheel supports 20 were to be rotated about the folding assemblies 22 before rotation of the handle supports 24 about the folding assemblies, then the frame 12 would appear in a partially folded state as shown in the front elevations view of FIG. 5 and the side elevational view of FIG. 6. In a fully folded state, both the forward wheel supports 20 and the handle supports 24 have been rotated about the folding assemblies 22 to be positioned in close proximity to the rear wheel supports 30 as shown in the side elevational view of FIG. 7.

As shown in FIG. 8, each of the folding assemblies 22 includes a forward rotatable member 35′ having a disk 36′ with a notch 38′ and an arm 40′, and a rearward rotatable member 35″ having a disk 36″ with a notch 38″ and an arm 40″. The disks 36′ and 36″ and the arms 40′ and 40″ are depicted in FIG. 8 as being part of a single formed piece; however, in other implementations the disks and arms are individual pieces that are fixedly attached together. The rotatable members and 35′ and 35″, along with a corresponding one of the rear wheel supports 30, are contained between left and right slotted halves of a housing 42 that allow the arms 40′ and 40″ to protrude outside of the housing. The inside wall of each half of the housing 42 has recess 42 a sized and shaped such that when the two halves of the housing are positioned together, the recesses for a cavity to securely receive the upper free-end portion of the rear wheel support 30 therein. The disks 36′ and 36″ each have a central aperture 41′ and 41″, respectively, sized to receive a bushing 43 therethrough having a length longer than the cumulative thickness of the two disks. When the folding assembly 22 is assembled, the disks 36′ and 36″ are arranged facing each other with the bushing 43 extending through the aligned apertures 41′ and 41″ of the disks, and this subassembly is positioned in a slot 30 b in the enlarged, upper free-end portion of the real wheel support 30. The slot 30 b has a forward to rearward orientation. A central aperture 43 b of the bushing 43 is aligned with a pair of opposing inward and outward side apertures 30 c of the rear wheel support 30, transverse to the orientation of the slot 30 b, and the left and right slotted halves of the housing 42 clamp around the slotted upper free-end portion of the rear wheel support 30. The left and right slotted halves of the housing 42 have opposing apertures 42 b, which align central with the central aperture 43 a of the bushing 43, such that a bolt 44 extends fully through the apertures 42 b of the halves of the housing 42, through the aperture 30 c of the rear wheel support 30, and through the central aperture 43 a of the bushing 43. A nut 44 a is threaded onto the threaded end of the bolt 44 to hold the assembly together with the disks 36′ and 36″ freely rotatable on the bushing 43. With this assembly, the bolt 44 and nut 44 a hold the left and right slotted halves of the housing 42 securely clamped together with the slots of the housing having the arms 40′ and 40″ extending therethrough. The arm 40′ extends forwardly through the forward opening of the slot 30 b and the other arm 40″ extends rearwardly through the rearward opening of the slot 30 b in the rear wheel support 30.

When the folding assemblies 22 are in the fully unfolded state, as shown in FIG. 9, the disks 36′ and 36″ of the folding assembly are locked in place by components positioned internal to the rear wheel supports 30 including a slidably mounted head 50 with a tip 52 inserted into the notches 38′ and 38″ as shown in FIG. 10. In FIG. 10, a cover portion 30 d of the upper free-end portion of the rear wheel support 30 is shown removed in order to better illustrate the components of the folding assembly 22 contained therein. The cover portion 30 d is attached to the other portion of the free-end portion of the rear wheel support 30 by a bolt 30 e, as seen in FIG. 9. The lever 34 is pivotally mounted to the rear wheel support 30 and the head 50 is mechanically linked to the lever 34 so that when the lever 34 is pulled upward and inward as depicted by the arrows R1 in FIG. 5, the head 50 is moved away from the disk 36′ and 36″, thereby causing the tip 52 to be retracted and disengaged from the notches 38′ and 38″. The disks 36′ and 36′ are then free to rotate on the bolt 44 and hence allow folding of the front wheel support 20 and the handle support 24 about the rear wheel support 30 in a clam shell movement, as will be explained in greater detail below.

The head 50 further includes a base 54, which rests against one end of a spring 56. The other end of the spring 56 rests against an internal support 58 inside the rear wheel support 30 such that the spring provides a force adequate to bias the tip 52 into an engaged state within the notches 38′ and 38″ of the disks 36′ and 36″ when the folding assembly 22 is in the fully unfolded state. While supplying a force to the head 50 to keep the tip 52 in the notches 38′ and 38″, the force is not so great as to require undue force to be applied to the lever 34 by the user to retract and disengage the tip from the notches when the folding assembly is to be folded.

The internal support 58 is coupled to or may be an integral part of the rearward free-end 30 a of the rear wheel support 30 to couple the folding assembly 22 to the rear axle assembly 14. As shown in FIGS. 11 and 12, for each of the folding assemblies 22 on the left and right sides of the stroller 12, the front wheel support 20 is bolted onto the arm 40′ of the forward rotatable member 35′ using a pair of bolts 60, and the handle support 24 is bolted onto the arm 40″ of the rearward rotatable member 35″ using a pair of bolts 62.

In the fully folded state of the stroller 12, both the front wheel support 20 and the handle support 24 are moved into close proximity to the rear wheel support 30. As shown in FIG. 12, in the fully folded state, the tip 52 of the head 50 is retracted and disengaged from the notch 38′ of the forward rotatable member 35′ and the notch 38″ of the rearward rotatable member 35″. In the fully folded state, both the front wheel support 20 and the handle support 24 are free to rotate independently of the other about the bolt 44 of the folding assembly 22 so that the notches 38′ and 38″ can be brought back into alignment with the tip 52 of the head 50 to consequently secure the stroller 12 into the fully folded state.

From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. For instance, the depicted implementation used the bolt 44 and nut 44 a assembly to rotatably couple the forward rotatable member 35′ and the rearward rotatable member 35″ together with a corresponding one of the rear wheel supports 30. In other implementations, pivot members other than the bolt-nut assembly may be used, including pin assemblies. As another example, in the depicted implementation, the rear wheel supports 30 supported the bolt 44 on which the rotatable members 35′ and 35″ were rotably mounted. In other implementations, either the front wheel support 20 can support the bolt 44 and have the rotatable members 35′ and 35″ rotatably mounted thereon with the arms 40′ and 40″ each fixedly attached to one of the handle support 24 and the rear wheel support 30 such that the handle support and the rear wheel support fold about the front wheel support, or the handle support 24 can support the bolt 44 and have the rotatable members 35′ and 35″ rotatably mounted thereon with the arms 40′ and 40″ each fixedly attached to one of the front wheel supports 20 and the rear wheel support 30 such that the front wheel support and the real wheel support fold about the handle support. As a further example, the rotatable members 35′ and 35″ were depicted as including the disks 36′ and 36″, however, in other implementations the rotatable members 35′ and 35″ may have other shapes. As an additional example, the depicted implementation aligned the tip 52 of the spring loaded head 50 of each folding assembly 22 with the notches 38′ and 38″ of the disks 36′ and 36″ to secure the stroller 12 into the fully folded state. In other implementations, each folding assemblies 22 can use a pin or other member that is inserted into holes in each of the disks 36′ and 38″ to hold the front wheel supports 20, the handle supports 24, and the rear wheel supports 30 unfolded state. Accordingly, the invention is not limited except as by the appended claims. 

We claim:
 1. A foldable stroller comprising: a folding assembly comprising: a first rotatable member comprising a first plate; and a second rotatable member comprising a second plate; wherein each of the first rotatable member and the second rotatable member are rotatably mounted on a pivot member and configured to pivot symmetrically about the pivot member along a common pivot axis, the pivot member comprising a rear wheel support for the foldable stroller; wherein when the first rotatable member is locked into a stationary position, the second rotatable member is also locked into a stationary position via a retractable tip extended from the pivot member, and when the first rotatable member and second rotatable members are released via the retractable tip retracted within the pivot member, each of the first rotatable member and second rotatable member pivot about the pivot member, the retractable tip being manipulated by a lever adjacent to the rear wheel support; wherein the first plate and the second plate are arranged in a face-to-face juxtaposition, and wherein the juxtaposed faces of the first plate and the second plate abut and slide along one another.
 2. The foldable stroller of claim 1, further comprising: a front wheel support; a rear wheel support; and a handle member.
 3. The foldable stroller of claim 2, further comprising at least one front wheel coupled to the front wheel support.
 4. The foldable stroller of claim 3, wherein the at least one front wheel comprises two front wheels.
 5. The foldable stroller of claim 2, further comprising at least one rear wheel coupled to the rearwheel support.
 6. The foldable stroller of claim 2, wherein the front wheel support is coupled to one of the first rotatable member, the second rotatable member, and the pivot member.
 7. The foldable stroller of claim 6, wherein the rear wheel support is coupled to a different second one of the first rotatable member, the second rotatable member, and the pivot member.
 8. The foldable stroller of claim 7, wherein the handle member is coupled to another different third one of the first rotatable member, the second rotatable member, and a third rotatable member.
 9. The foldable stroller of claim 8, wherein the handle member is pivotable with respect to the front wheel support.
 10. The foldable stroller of claim 7, wherein the rear wheel support is pivotable with respect to the front wheel support.
 11. The foldable stroller of claim 1, further comprising a pivot anchor assembly comprising a first portion confronting a second portion and being spaced from the second portion along the pivot axis, the pivot member extending between the first portion of the pivot anchor assembly and the second portion of the pivot anchor assembly.
 12. The foldable stroller of claim 1, further comprising: a second folding assembly comprising: a third rotatable member comprising a third plate; and a fourth rotatable member comprising a fourth plate; wherein each of the third rotatable member and the fourth rotatable member are rotatably mounted on a second pivot member and configured to pivot symmetrically about the second pivot member along a common second pivot axis; wherein the third plate and the fourth plate are arranged in a second face-to-face juxtaposition, and wherein the juxtaposed faces of the third plate and the fourth plate abut and slide along one another.
 13. The foldable stroller of claim 12, wherein the pivot axis and the second pivot axis are coaxially aligned.
 14. A foldable stroller comprising: a first folding assembly comprising: a first rotatable plate comprising a first central aperture and a first planar arm projecting from the first rotatable plate; a second rotatable plate comprising a second central aperture and a second planar arm projecting from the second rotatable plate; and a pivot member, wherein the first rotatable plate and the second rotatable plate are rotatably mounted on the pivot member, the pivot member comprising a rear wheel support for the foldable stroller, the pivot member comprising: a bushing that extends through the first central aperture and the second central aperture; wherein when the first rotatable member is locked into a stationary position, the second rotatable member is also locked into a stationary position via a retractable tip extended from the pivot member, and when the first rotatable member and second rotatable members are released via the retractable tip retracted within the pivot member, each of the first rotatable member and second rotatable member pivot about the pivot member, the retractable tip being manipulated by a lever adjacent to the rear wheel support; wherein the first rotatable plate and the second rotatable plate are arranged in a face-to-face juxtaposition; and wherein the juxtaposed faces of the first rotatable plate and the second rotatable plate abut and slide along one another.
 15. The foldable stroller of claim 14, further comprising: a front wheel support; at least one front wheel coupled to the front wheel support; a rear wheel support; and at least one rear wheel coupled to the rear wheel support; and a handle member.
 16. The foldable stroller of claim 15, wherein the front wheel support is coupled to one of the first rotatable member, the second rotatable member, and the pivot member; wherein the rear wheel support is coupled to a different second one of the first rotatable member, the second rotatable member, and the pivot member; and wherein the handle member is coupled to another different third one of the first rotatable member, the second rotatable member, and a third rotatable member.
 17. The foldable stroller of claim 14, wherein the bushing facilitates a symmetric rotation of the first rotatable plate and the second rotatable plate about a common pivot axis.
 18. The foldable stroller of claim 14, further comprising a pivot anchor assembly comprising a first portion confronting a second portion and being spaced from the second portion along the pivot axis, the pivot member extending between the first portion of the pivot anchor assembly and the second portion of the pivot anchor assembly.
 19. The foldable stroller of claim 14, further comprising: a second folding assembly comprising: a third rotatable member comprising a third plate; and a fourth rotatable member comprising a fourth plate; wherein each of the third rotatable member and the fourth rotatable member are rotatably mounted on a second pivot member and configured to pivot symmetrically about the second pivot member along a common second pivot axis; wherein the third plate and the fourth plate are arranged in a second face-to-face juxtaposition, and wherein the juxtaposed faces of the third plate and the fourth plate abut and slide along one another.
 20. A foldable stroller comprising: a folding assembly comprising: a first rotatable member comprising a first plate; a second rotatable member comprising a second plate; a pivot member, wherein each of the first rotatable member and the second rotatable member are configured to pivot symmetrically about the pivot member along a common pivot axis, the pivot member comprising a rear wheel support for the foldable stroller; and a pivot anchor assembly comprising a first portion confronting a second portion and being spaced from the second portion along the pivot axis, the pivot member extending between the first portion of the pivot anchor assembly and the second portion of the pivot anchor assembly; wherein when the first rotatable member is locked into a stationary position, the second rotatable member is also locked into a stationary position via a retractable tip extended from the pivot member, and when the first rotatable member and second rotatable members are released via the retractable tip retracted within the pivot member, each of the first rotatable member and second rotatable member pivot about the pivot member, the retractable tip being manipulated by a lever adjacent to the rear wheel support; wherein the first plate and the second plate are arranged in a face-to-face juxtaposition, and wherein the juxtaposed faces of the first plate and the second plate abut and slide along one another. 